package java_cup;

/**
 * This class represents one part (either a symbol or an action) of a
 * production. In this base class it contains only an optional label string that
 * the user can use to refer to the part within actions.
 * <p>
 * 
 * This is an abstract class.
 * 
 * @see java_cup.production
 * @version last updated: 11/25/95
 * @author Scott Hudson
 */
public abstract class production_part {

	/*-----------------------------------------------------------*/
	/*--- Constructor(s) ----------------------------------------*/
	/*-----------------------------------------------------------*/

	/** Simple constructor. */
	public production_part(String lab) {
		_label = lab;
	}

	/*-----------------------------------------------------------*/
	/*--- (Access to) Instance Variables ------------------------*/
	/*-----------------------------------------------------------*/

	/**
	 * Optional label for referring to the part within an action (null for no
	 * label).
	 */
	protected String _label;

	/**
	 * Optional label for referring to the part within an action (null for no
	 * label).
	 */
	public String label() {
		return _label;
	}

	/*-----------------------------------------------------------*/
	/*--- General Methods ---------------------------------------*/
	/*-----------------------------------------------------------*/

	/**
	 * Indicate if this is an action (rather than a symbol). Here in the base
	 * class, we don't this know yet, so its an abstract method.
	 */
	public abstract boolean is_action();

	/* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */

	/** Equality comparison. */
	public boolean equals(production_part other) {
		if (other == null)
			return false;

		/* compare the labels */
		if (label() != null)
			return label().equals(other.label());
		else
			return other.label() == null;
	}

	/* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */

	/** Generic equality comparison. */
	@Override
	public boolean equals(Object other) {
		if (!(other instanceof production_part))
			return false;
		else
			return equals((production_part) other);
	}

	/* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */

	/** Produce a hash code. */
	@Override
	public int hashCode() {
		return label() == null ? 0 : label().hashCode();
	}

	/* . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . */

	/** Convert to a string. */
	@Override
	public String toString() {
		if (label() != null)
			return label() + ":";
		else
			return " ";
	}

	/*-----------------------------------------------------------*/

}
